THE VARIATIONS OF THE MEDIAN NERVE Nervus medianus' un varyasyonları

ARAŞTIRMALAR(Research Reports)

THE VARIATIONS OF THE MEDIAN NERVE Nervus medianus ' un

Nihat EKİNCݹ, Erdoğan UNUR², Harun ÜLGER2, Şevki KABAK³

Özet

Amaç: Bu çalışmanın amacı n. medianus'ıın oluşum varyasyonlarını belirlemekti.

Gereç ve Yöntem: Bu çalışmada, 22 kadavranın üst ekstremitesindek i n. medianus'lar disekte edilerek incelendi.

Bulgular: İncelediğimiz 22 vakanın 17 'sinde n. medianus klasik kaynaklarda belirtildiği gibifascicııfııs medialis ve

laıeralis 'den gelen iki kökün birleşmesinden oluşmakta

idi. N. ınedianus varyasyonu görülen beş vakada ise ya

fascicıılııs lateralis 'den ya da n. ınusculocuıeneııs 'dan gelen üçüncü bir kök n. medianııs yapısına katılmaktaydı.

Varyasyonlu beş vakanın dördünde üçüncü kök n.

musculocuıeneus 'dan doğuyor ve n. medianııs yapısına katılıyordu. Beş vakanın birinde üçüncü kök fasciculus lateralis'in terminal dallarını verdiği yerden doğuyor ve n. medianus 'un iki kökünün birleştiği yerin distalinde bu sinire katılıyordu.

Sonuç: Sonuç olarak, aksillar bölge cerrahisinde n.

ınedianus varyasyonlarının bilinmesinin aksiller bölge

ameliyatı sırasında cerrah için faydalı olacağını

umuyoruz.

Anahtar Kelimeler: Anatomi, Nervııs medianııs

The median nerve is formed by two roots from both the medial and the lateral cords. The lateral root of the median nerve and its medial root join anterior to the third part of the axillary artery to establish the median nerve ( 1,2). it has been reported that some

fıbers from ali branches ofthe brachial plexus could join to form the median nerve (3).

Previous reports have showed that the varıatıons

might be in the numbers of the median nerve roots and between the median and musculocuteneus nerve

Erciyes Üniversitesi Tıp Fakültesi 38039 KA YSERI Anatomi. Doç.Dr.¹, YDoç.Dr.¹.

Ortopedi ve Travmatoloji. Y.Doç. Dr. ³. Geliş tarihi: I 4 Haziran I 999

Abstract

Aim: The aim of this study was to de/ermine ıhe

variations of forınation of the median nerve.

Materials and Metlıod: Median nerves on ıhe upper

extreınities of 22 cadavers were investigated ıısing

dissection technique.

Resıılts: The ınedian ner,ıe wasformed by ıwo rooıs which were coıning /rom mediaf and lateral cords in 17 of 22 cases as il has been described in cfassical texts. in jive cases which had variations, a third rooı was joinin.g ıhe

median nerve. The third rooı was arising either ji-om the lateral cord or ıhe musculocuıaneous nerve. lnfoıır of the

fıve cases with variations, the third root was arisingfrom distal par/ of the mııscıılocııtaneoııs nerve andjoining the median nerve. in one of the fıve cases, the third rooı was arising ji-om the par! where the lateral cord was giving the terminal branches oııt and it was joining the median nerve distally after the joining point of two main roots.

Conclıısion: We conc/ııde thaı it might be more ıısefıt! if the surgeon knows aboııt these variations dııring the

sıırgery of ıhe axillary region.

Key Words: Anatomy, Median nerve

connections ( 4,5). The lateral cord shows more variations in origin (3,6). Some of the fıbers of the median nerves lie with musculocutaneous nerve before joining the median nerve (3,7,8). Sometimes the lateral root of the median nerve might be partially or completely absent (9). Some authors have reported that while the median nerve usually consists of two roots (2,3), sometimes it has a third one (4). lt has also been reported that two roots of the median nerve could arise directly from superior and middle trunks (5, l O).

During a dissection for demonstration to medical students in the anatomy laboratory of Erciyes University Medical Faculty a variation ofthe median nerve in the right brachial plexus was found in a 50

185 Erciyes Tıp Dergisi (Erciyes Medical Journal) 22 (4) 185-187, 200()

year old male cadaver (8). After that, we investigated the variations in the formation of the median nerve in 22 brachial plexus of22 cadavers in

mır laboratory collection. MATERIALS AND METHOD

The brachial plexus of 22 upper extremites from both sides were dissected and the variations of the roots ofmedian nerve were investigated. Ifthere was any variation in number and position of the roots, their fıgures were drawn. The fındings were evaluated according to the literature.

RESULTS

The normal median nerve was seen in 17 (77.3%) out ofthe 22 cases. These were formed by the fusion of two roots; one of them from the medial cord, another from the lateral cord. There were median nerve variations in fıve cases (22.7%). The median nerves were forıned by the connection ofthree roots in these cases. in four ofthe fıve cases (18.2%), the third root was arising frorn the musculocutaneous nerve after muscular branches and joining the

ınedian nerve at the distal part (fıg 1 ). In one case (4.5%), the third root was arising from the lateral cord bet:ween the rnusculocutaneous nerve and the lateral root. This root was joining tlıe median nerve at the distal part (Fig 2).

Figııre 1. Tlıe variatioıı of tlıe left brachial plexus: 111. bıccps braclıii (111bb), 111. deltoideus (111d), m. coracobrachia lis (nıcb);

nıusculocutaııeous ııerve ( 1 ), lateral root of tlıe ınedian ııerve (2), nıedial root of the ınediaıı nerve (3), lateral cord (4), medial cord (5), 111edial cutaııeous ııerve ofbrac hii (6), medial cutaııeous ııerve of forerın (7), ulııar ııerve (8), 111edian ııerve (9), the variated second braııch conıing fronı the 111usculocutaııeous ııerve to the mediaıı ncrve ( 1 O), tlıe inııervatiııg nerve fibers of biceps braclıii

( 1 1)

The variations of the nıediaıı ııerve

1

Figure 2. Tlıe variation of tlıe right brachial plexııs: nı. biceps braclıii (111bb), nı. deltoideus (ınd); ınusculocutaııeous ııerve (!), the secoııd variated braııch conıing froııı tlıe lateral cord to median ııerve (2), ınediaıı ııerve (3), ulııar nerve (4), nıedial root of tlıe ınediaıı ııerve (5), lateral root of tlıe ıııcdiaıı ııervc (6)

!atemi cord (7), posterior cord (8), ınedial cord (9).

DISCUSSION

in classical texts, it has been reported that the rnedian nerve is forrned by two roots, medial and lateral ( 1-3). However, there is some inforınatioıı

abmit variations of this nerve (5, 1 1 -15). it has alsa been reported that the lateral root of the median nerve might be completely or partially absent (6).

it was reported that most of the variations were seen in tlıe peripheral branches of braclıial plexus (3,6- 8, I0, 14). The incidence ofmedian nerve variations were reported between 8-36% (3, 14). it was found to be 22.7% in this study. Jn the cases that have peripheral nerve variations , some nerve fıbers go together witlı a neighbouring nerve teınporarily and join the original nerve at the distal part (6). it was reported that some nerve fıbers usually arose from the ınusculocutaneous nerve after passing tlırough

the coracobrachial muscle and join the median nerve. (3,6-8,1 l, 14). There were similar variations in four cases ( 18.2%) in the present study. Sarsılmaz

et al., (7) and Sargon et al., ( 4) reported that the median nerve is formed by three roots, two of them from tlıe lateral cord and one from the medial cord.

Only in one case ( 4.5%), we found a median nerve with three roots, two ofwhich were coming from the lateral cord, while the third was coming from the medial cord.

Erciye..-Tıp Dergisi (Erciyes Medical Journal) 22 (4) 185-187, 20()() 186

Ekiııci, Uıııır, Ülger, Kabak

it has been reported that the anatomy of brachial plexus could be iınportant in the surgery and treatment of the axillary region (14, 15). Moreover, it could also be important to know about nerve variation incidence in this area. Any surgical operation without suffıcient knowledge about nerve variations could cause nerve damage. For this reason, during the dissection and reconstruction of the axillary region, it is also necessary to take the median nerve variations into consideration.

REFERENCES

/. Dere F. Anatomi. Okullar Pazarı. Kitabevi, Adana 1990, s 99.

2. Wiliiams Pl, Warwick R, Banister LH. Gray's A natomy, Churchi/1 livingstone, Edinbıırg

1989, pp l J 30-1135.

3. Arıncı K, Elhan A. Anatomi il. cilt Güneş

Kitabevi, Ankara 1997, ss 210-221.

4. Sargan MF, Uslu SS, Çelik HH, Akşit D. A variation of the median nerve at the /eve/ of brachia/ p/exus. Bul/etin de I Assosiation des Anatomistes /995; 79: 25-26.

5. Tsikaras PD, Agiabasis AS, Hytiroglou. A variation in theformation ofthe brachial pfexus characterised by the absence of' C 8 and T I )ibers in the trıınk of the median nerve. Bul/etin de J Assosiation des Anatomistes 1983; 67:

501-505.

6. Mıımenthaler M, Sch/iack H Peripheral Nerve lesions. Diagnosis and Therapy. Thieme Medical Publishers ine., New York 1991, pp 157-160.

7. Sarsılmaz M, Şendemir E, Çelik HH,

Gümüş alan

Y.

11: 161-165.

8. Ekinci N, Unıır E, Ülger H. Bir nervııs medianus varyasyonu. Erciyes Tıp Dergisi J 998; 20: 166-

168.

9. K/ine DG, Judice CM. Operative management of selected brachia/ p/exus lesi ons. J Neurosurg

/983; 58: 631- 649.

10. Nakatani T, Tanaka S. Two rare anomalies of the hrachiaf p/exus. J Anat 1998; 192: 303-304.

11. Nakatani T, Tanaka S. Absence of the

mıısculocutaneus nerve with innervation of coracobrachialis, bicepsbrachii, brachialis and the /ateral border of the forearın by branches .(rom the /atera/ cord of the brachial plexus. J

Anat 1997; 191: 459-460.

12. Arman C, Karman E, Tunç A, Başa/oğlu H, Buldan Z. İnsanda plexus brachia/isin oluşumu

ve dallarının orijinindeki morfolojik

değişiklikler. il. Anatomi Kongresi Bildiri ve Poster Özetleri, Adana 1995; p 52.

13. Şahin B, Bilgiç S, Uzun A. Yenidoğanda N.

medianus'un seyri ve dal/anışının morf'ometrik incelenmesi. On Dokuz Mayıs Ünversitesi Tıp

Dergisi 1994; il : 101-/08.

14. Kerr AT The brachial plexus ofnerves in man, the variations in itsformation and branches. ılın

J Anat 1918; 23: 285-399.

15. Siegel DB, Gelberman RH. Median Nerve: Applied Anatomy and Opera/ive Exposııre. in:

Gelberman RH (ed). Operative nerve repair and reconstruction. Vol. l, J.B. lippincott Coıııp,

New York 199/, pp 365-391.

187 Erciyes Tıp Dergisi (Erciyes Medica/ Joıırnal) 22 (4) /85-187, 2000